JPS62232601A - Plastic clad optical transmission fiber - Google Patents

Abstract

PURPOSE:To obtain the titled fiber having less transmission loss and excellent moisture-resisting and a water-proof properties and strength, and having a less tendency for generating protrusion at a connector part by coating a core with a specific fluorine contg. polymer which is soluble to a solvent followed by curing it. CONSTITUTION:The titled fiber comprises the core composed of qualtz glass or an optical glass and the clad composed of a cured polymer of the fluorine contg. polymer which is soluble to a solvent and has the curable moiety. The used fluorine contg. polymer includes an addition type polymer and a polycondensation type polymer. The addition type polymer includes the addition polymer or addition copolymer of a fluorine contg. unsatd. compd., and has the curable moieties of hydroxy and epoxy groups and halogen atom. The polycondensation type polymer includes an epoxy resin having a fluorine contg. bifunctional group or condensate of diol and diisocyanate contg. the fluorine atom, etc., which is capable of forming ester, urethane and urea binding, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plastic clad optical transmission fiber with improved characteristics such as low transmission loss and excellent water resistance.

Conventional technology: Plastic clad optical transmission fibers (hereinafter referred to as PCFs), which have a core of quartz glass or optical glass and a plastic cladding, have been known for a long time, and have a particularly large numerical aperture (NA) and low transmission loss. Therefore, it is expected to be used in a wide range of fields such as optical communication, image transmission, and light guides.

Since the refractive index of the PCF changes by changing the type of plastic used for the cladding, it is possible to obtain PCFs with various numerical apertures.

When the core is made of especially high-purity quartz glass, the refractive index is as low as 1.458, so the plastic used as the cladding material must be selected from a material with a refractive index lower than this. As for the properties as a cladding material, it is necessary to satisfy the following conditions: (a) colorless and transparent, (b) adhesion to the core, and (c) excellent cladding properties.

Therefore, the range of selection becomes extremely narrow.

Examples of clad materials that satisfy the above conditions include dimethyl silicone, fluororesin, etc. PCFs using dimethyl silicone are well known, and such PCFs are widely used in practical use. In addition, regarding fluororesin as a clad material, PCF (Japanese Patent Publication No. 48-2
No. 566! vA), A6 and TE): PCF using a ly fluoroethylene-vinylidene fluoride copolymer (see Japanese Patent Application Laid-open No. 52849/1984) and the like have been proposed.

[Problems to be Solved by the Invention] As mentioned above, although silicone PCF using dimethyl silicone as the cladding material may have satisfactory optical properties, the strength of silicone is low and the hardness is also low. Strength is 3-40kg/cm2,
Since the hardness is JIS A20-80, it has the disadvantage that it is difficult to connect with a connector. -20°C to +80°C, especially if adhesive is used to connect with the connector.
In the heat cycle test, stress acts on the interface due to the difference in expansion coefficient between the quartz glass core and the cladding material, causing the tip of the strand to protrude. Furthermore, as a unique property of silicone resin, it has a relatively high moisture permeability coefficient, and in silicone PCF under high temperature and high humidity environments, moisture easily penetrates through the silicone and enters the interface between the core and cladding. It also has the disadvantage of promoting surface flaw growth and reducing fiber strength.

On the other hand, a fluororesin PCF using a fluororesin as a cladding material has high strength and does not easily cause the phenomenon of protrusion from the connector, but it does not have excellent optical transmission characteristics. This is due to poor adhesion between the quartz glass core and the fluororesin.

In other words, fluororesin is generally difficult to dissolve in solvents, so instead of solution-based coating, the core is coated with fluororesin by extrusion molding, which can cause poor adhesion and reduce transmission loss. I'm making it bigger. Even if fluororesin dissolves in a specific solvent, only 10 to 20% by weight dissolves, and it is difficult to adjust the viscosity, boiling point, etc. of the solution, and coating as a solution is difficult. There was a point.

The present inventors, in order to solve such conventional problems,
After further research and consideration, we discovered that a specific solvent-soluble fluorine-containing polymer was discovered, and by coating the core with it and curing it, we were able to obtain an optical transmission fiber without the above-mentioned drawbacks.

The present invention was made based on such knowledge, and
The object of the present invention is to provide a plastic clad optical transmission fiber that has low transmission loss, excellent moisture resistance, water resistance, and strength, and is less likely to protrude at a portion of the connector.

[Means for solving the problems] That is, the plastic clad optical transmission fiber of the present invention has a core made of quartz glass or optical glass,
The cladding is characterized by being made of a cured product of a solvent-soluble fluorine-containing polymer having a cured portion.

As the solvent-soluble fluoropolymer having a hardened part used in the present invention, addition polymer type and condensation polymer type can be used. Examples of addition polymers include addition polymers or addition copolymers of fluorine-containing unperturbed compounds, which contain hydroxyl groups, epoxy groups, carboxyl groups, acid amide groups, ester groups, unsaturated bonds, active hydrogen, and halogens. Examples of 1a polymer type include epoxy resins with fluorine-containing difunctional groups, diols containing fluorine, dibasic acids, dibasic acid anhydrides, diisocyanates, etc. Examples include condensates that form ester bonds, urethane bonds, urea bonds, etc.

Furthermore, these fluorine-containing polymers have good adhesion to the quartz glass core, strength as a cladding, hardness,
From the viewpoint of easy availability, addition polymer systems such as copolymers of fluoroolefins and hydrocarbon vinyl ethers are preferred. Such a fluoroolefin-vinyl ether copolymer contains 30 to 70 units based on fluoroolefin and vinyl ether, respectively.
The intrinsic viscosity [η
] is preferably about 0.06 to 2.0 d (2/g). Also, it is desirable to contain units based on hydroxyl group-containing vinyl ether or glycidyl vinyl ether in a proportion of 30 mol % or less.

Tetrafluoroethylene, chlorotrifluoroethylene, and mixtures thereof are suitable as the above-mentioned fluoroolefin component, and as the vinyl ether component, linear, branched, or cyclic alkyl groups having about 2 to 8 carbon atoms are suitable. Suitable are alkyl vinyl ethers having the following: cyclohexyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, and the like. Moreover, vinyl ether of a fluorine-containing polymer can also be exemplified as a suitable example for the purpose of lowering the refractive index.

Furthermore, these copolymers preferably contain a comonomer component that provides a curing site. Examples of the comonomer that provides such a curing site include ω-hydroxybutyl vinyl ether and hydroxypropyl vinyl ether. Hydroxyl group-containing alkyl vinyl ethers, such as hydroxyl group-containing alkyl vinyl ethers, and functional group-containing vinyl ethers, such as glycidyl vinyl ether, are suitable.

In addition, if necessary, a copolymer containing other vinyl monomers that can be copolymerized with the above copolymerization components, such as acrylic esters, methacrylic esters, alkyl vinyl esters, styrene, or fluorine-substituted products thereof, etc. There may be.

The above-mentioned copolymers can be produced by causing a copolymerization reaction by allowing a polymerization initiator or a polymerization initiation source such as ionizing radiation to act on a monomer mixture of a predetermined ratio in the presence or absence of a polymerization medium. Manufactured by.

The fluoropolymer having a hardening site produced in this way is solvent-soluble, and is prepared by dissolving it in a solvent to prepare a paint-like clad composition, which is applied to the quartz glass core, and then cross-linked and cured. It is used as a hardened body as a cladding.

The solvents used here include ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate and butyl acetate, toluene, and xylene.

Examples include aromatic compounds such as carbon, aliphatic hydrocarbon compounds such as octane and hexane, and the like. It is desirable to use these in combination as appropriate.

When preparing a paint-like cladding composition by dissolving a fluoropolymer in a solvent, a curing agent of a polyfunctional compound having reactivity with the curing site of the fluoropolymer is added to the fluoropolymer 100. It is blended in a ratio of 0.1 to 100 parts by weight, preferably 0.5 to 50 parts by weight. Further, a curing aid or a curing catalyst can be appropriately blended as necessary. When preparing a cold-curable cladding composition using a fluorine-containing polymer whose curing site is a hydroxyl group, polyisocyanates or metal alkoxides can be used as the curing agent. In addition, when this cladding composition is made into a heat-curing type, a melamine curing agent, a urea resin curing agent, a polybasic acid curing agent, etc., which are used in ordinary heat-curing acrylic paints, are used as the curing agent. can do.

Examples of the melamine curing agent include butylated melamine, methylated melamine, epoxy-modified melamine, etc.
Depending on the application, various degrees of modification from O to 6 can be used, and the degree of self-condensation can also be selected as appropriate. Further, as the above-mentioned urea resin curing agent, methylated urea, butylated urea, etc. can be used. Further, as the polybasic acid curing agent, long-chain aliphatic dicarboxylic acids, aromatic polycarboxylic acids or anhydrides thereof, block polyvalent incyanates, etc. can be used. When using these melamine curing agents or urea curing agents, curing can be accelerated by adding an acidic catalyst.

When preparing a cladding composition using a fluorine-containing polymer whose curing site is an epoxy group, amines, carboxylic acids, phenols, alcohols, etc. can be used as curing agents. Multihydroxy compounds, especially non-aromatic diols, can be used as auxiliaries.

In the present invention, when the core is made of silica glass, the refractive index of the cladding must be 1.45 or less,
Preferably it is 1.44 or less.

Thus, by arbitrarily changing the refractive index of the cladding, a PCF with an arbitrary numerical aperture can be obtained, but since the fluorine content can be changed by appropriately selecting the fluorine-containing polymer, the numerical aperture can be changed. A variety of PCFs can be manufactured with different values.

In the present invention, the thickness of the cladding layer formed on the core quartz glass or optical glass is usually 5 to 10 μl, but in order to make it useful as a protective layer, it is about 10 to 10 μl thick.
A suitable thickness is 50 μm. The cladding forming force method is not particularly limited.

Immediately after spinning quartz glass or optical glass as a core, a paint-like cladding composition is applied or dipped,
It is hardened by heating etc. to form a hard body. Thus,
A wire having a core formed with a cladding is usually further coated with a protective coating layer to form a core wire. Suitable materials for such a covering layer include, but are not limited to, nylon, thermoplastic fluororesin, acrylic urethane, epoxy urethane, etc. Also, there is no buffer between the cladding layer and the covering layer. By providing a layer, it is also possible to alleviate stress.

The thus obtained PCF of the present invention can be uniformly applied easily and has good adhesion because a solvent-soluble fluorine-containing polymer is applied as a cladding material to the quartz glass or optical glass core.

Moreover, the cured product obtained by the curing treatment has high adhesive strength with the adhesive in a part of the connector, suppresses the occurrence of fiber protrusion as described above, has good water resistance, and has excellent transmission characteristics. .

[Example] Example 1 A terpolymer of chlorotrifluoroethylene, ethyl vinyl ether and hydroxybutyl vinyl ether, containing ff1 of chlorotrifluoroethylene/ethyl vinyl ether/hydroxybutyl vinyl ether
The f ratio is 81.3/28.4/10.3, and the intrinsic viscosity at 30°C in tetrahydrofuran is 0.10 d(
7 parts by weight of methylated melamine (°°Cymel 303", a product of Mitsui Toatsu Co., Ltd.) was added to a solution prepared by dissolving 1001 JL parts of a fluorine-containing polymer with a concentration of 2/g in 80 parts by weight of methyl ethyl ketone, and paratoluenesulfone as a catalyst. Acid 0.
A uniform paint-like cladding material composition was prepared by adding 5 parts by weight.

Next, this composition was prepared from a quartz glass base material with a diameter of 200 μm.
It is coated immediately after spinning fibers spun to mφ, and fired by passing through a heating furnace at a temperature of about 300°C for 1 second to form a cladding layer with a thickness of 20 pta consisting of the cured product, which forms a core-clad structure. I got the core line. This core wire was coated with nylon ('N-111140, manufactured by Daicel Corporation) by melt extrusion to form a coating layer, and the outer diameter was 0.9mm.
It was set as a PCF of φ.

As a result of measuring the optical characteristics of this PCF, the transmission loss (850 nm) was 10 dB/km, and the NA was 0.15. Further, after bonding this PCF and the connector with epoxy resin, a heat cycle test from -20°C to +80°C was conducted, and no fiber protrusion was observed. Further, as a water resistance test, the PCF was immersed in warm water at 80° C. for 200 hours, and the tensile strength of the PCF was then measured to be 800 kg/colole 2.

Furthermore, the refractive index of the fluorine-containing polymer as the cladding! The ID is 1.449.

Example 2 A terpolymer of tetrafluoroethylene, ethyl vinyl ether, and hydroxybutyl vinyl ether, comprising:
The content weight ratio of tetrafluoroethylene/ethyl vinyl ether/hydroxybutyl vinyl ether is 80.8/
29.5/3.7 and 30 in tetrahydrofuran.
A paint-like cladding material composition was prepared in the same manner as in Example 1 using a fluoropolymer having an intrinsic viscosity of 0.20 dQ/g at °C.

This composition was applied to a fiber made of quartz glass in the same manner as in Example 1, and fired to form a cured product to obtain a core wire with a cladding layer having a thickness of 20 μm. This core wire is coated with ethylene-tetrafluoroethylene copolymer (°゛Aflon C).
OP: manufactured by Asahi Glass Co., Ltd.) was coated by melt extrusion to form a coating layer to form a PCF with an outer diameter of 0.6 layer φ.

As a result of measuring the optical characteristics of this PCF, the transmission loss (850 nm) was 7 dB/km, and the NA was 0.
It was 35. Further, this PCF and the connector were bonded together using an epoxy resin, and a heat cycle test was conducted in the same manner as in Example 1, but no protrusion of the fibers was observed. Furthermore, in the same water resistance test as in Example 1, P
The tensile strength of CF was 590 kg/112 intestines.

Incidentally, the refractive index no of the cured product of the fluorine-containing polymer as the cladding is 1.412.

Comparative Example 1 In the same manner as in Example 1, dimethyl silicone (OF 10B, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied immediately after spinning fibers spun to a diameter of 200 μ layers φ from a quartz glass base material, and the fibers were heated at a temperature of about 400°C. The wire was fired by passing through a heating furnace for 1 second to obtain a core wire on which a cladding layer with a thickness of 50 μm was formed. This core wire was coated with nylon by melt extrusion to form a coating layer, resulting in a PCF having an outer diameter of 0.9 mm.

As a result of measuring the optical characteristics of this PCF, the transmission loss (850 nm) was 5 dB/km, and the NA was 0.
It was 39. Further, in a heat cycle test after bonding this PCF to a connector in the same manner as in Example 1, protrusion of 50 to 1000 μm was observed. Furthermore, in the water resistance test, the tensile strength of PCF was
It was 100 kg/-2 intestines.

Furthermore, the refractive index no of dimethyl silicone as the cladding is
is 1.410.

[Effects of the Invention] The plastic clad optical transmission fiber of the present invention has the advantage that the cladding layer has less transmission loss than a cured product of a specific fluoropolymer, and the fiber is less likely to protrude at the bonded portion with the connector. It has a great effect.

Generally, when a glass fiber has a scratch on its surface, stress is concentrated in that area, and deterioration due to moisture progresses from there. Therefore, as a plastic clad optical transmission fiber, it is necessary to avoid accumulation of moisture or hydroxyl groups on the core fiber made of quartz glass, and it is more desirable to use a material with low moisture permeability as the cladding material.

The cured fluoropolymer of the cladding layer in the present invention has poor affinity for moisture, and does not cause surface wetting or moisture permeation.

Therefore, it also has the excellent effect of not exhibiting a decrease in strength even under adverse environmental conditions, such as when used outdoors.

Furthermore, by changing the amount of fluorine contained in the clad material, the NA can be arbitrarily selected within the range of 0.1 to 0.4.

Claims (1)

[Claims] 1. A plastic clad optical transmission fiber in which the core is made of quartz glass or optical glass and the cladding is made of plastic, characterized in that the cladding is made of a solvent-soluble fluorine-containing polymer having a hardened portion. Plastic clad optical transmission fiber. 2. A solvent-soluble fluoropolymer having a curing site is
The plastic clad optical transmission fiber according to claim 1, which has at least one type of curing site selected from hydroxyl group, epoxy group, carboxyl group, acid amide group, ester group, unsaturated bond, active hydrogen, and halogen. 3. A solvent-soluble fluoropolymer having a curing site is
A copolymer of a fluoroolefin and a hydrocarbon vinyl ether, containing 30 to 70 mol% and 70 to 30 mol% of units based on fluoroolefins and vinyl ethers, respectively, and units based on hydroxyalkyl vinyl ethers or glycidyl vinyl ethers. 3. The plastic clad optical transmission fiber according to claim 1 or 2, which contains 30 mol% or less of.